Piston



Sept 9 1924- V v A. H. M. J. WARD PISTON Filed March 31 1924 D l M M M wH MD L mMAQWJ/mu,

I ARGHIBALD HENRY MONTGOMERY JOHN WARD, 0F MEREWORTH, N ID STONE,

ENGLAND.

PISTON.

Application filed March 31, 1924. Serial No. 703,222.

in which--lies a ring that bears against the bottom of the groove as well as against the cylinder wall. In this type of piston this ring (which hereunder is termed a bearing ring) in addition to functioning as an oil scraper, serves to relieve the skirt of contact with the cylinder wall, and it is particularly useful where the skirt is of aluminium alloyv or similar soft metal.

The object of the invention is to provide an improved construction which can be 'made shorter than usual and which will be freefrom binding or from creating excessive friction, and which will not be subject to fractures of the skirt.

The manner of carrying out the invention is illustrated in the accompanying drawings, in which Fi ure 1 is a central vertical section showing t 'e preferred construction of piston,

Figure 2 is an enlarged view showing the ring and adjacent parts of the piston skirt,

Figure 3 is a horizontal section on the line 33 of Figure 1', whilst Figures 4 and 5 are a side view and section of the skirt on an enlarged scale showing a detail,

Figure 6 is a section, and

Figure 7 a side elevation showing the application of the inventionto a skirtless piston.

Like letters indicate like parts throughout the drawings.

In the construction shown in Figures 1 to 5,'the piston is chiefly of conventional form having a skirt A which is preferably slit vertically at a number of points B in the well-known manner. The gudgeon pin bosses are shown at and preferably, to prevent weakness at these parts, no slits are, as a rule, formed in the skirt on the faces of the piston containing these bosses, but between the bosses, i. e. on those faceswhich within small limits less than the bore.

receive the thrustfrom the connecting rod and are herein termed the pressure faces, any suitable number of slits are made.

' N ear the bottom of the skirt is a land D which is of Smaller diameter than the cylinder bore. In this land is formed a groove D and in the groove is located the split bearing ring E. This bearing ring is of hard metal, such as cast iron, and its outside diameter. is that of the cylinder borearfir e bottom of the ring, i. e. the face E (Figure 2), bears against the bottom of the groove D on the pressure faces of the piston, i. e. along the arcs between the gudgeon pin bosses C. At a suitable distance along the silient, as is very desirable. The ring is located against twisting by means of a peg F.

If desired a spring ring may be arranged inside the skirt, to resist the compression of the ring E and the skirt, in the well-known manner.

Seeing that the piston must not project below the bottom of the cylinder at the bot tom of'the piston stroke, as otherwise the ring E would spring out of the cylinder mouth, the piston must generally be made shorter than is usually the case when a split skirt is used. As the piston heats up and the skirt tends to expand radially outwards,

this is prevented by the ring E, which, as 4 has been described, not only bears agalnst the cylinder wall, butbottoms at the specified places only on the oove D. For this reason the skirt is split as this allows the expansion of the metal of the skirt to take place without any binding. On the pressure faces of the piston, i. e., those faces which receive the thrust from the connecting rod, the slits B can be comparatively long, but, on the sides on which are located the bosses C, only very short slits can be made, and I have found that, with a short piston, if the ring E bottoms in the groove the whole way round, the tongues formed between the slits in the shirt below the gudgeon pin bosses actually break oil. These fractures are due to the insulhcient springiness of the skirt tongues at this part, and to the rapid change of section at these points which concentrates the stresses along lines below the gudgeon pin bosses. These Tractures and excessive binding of the ring E are prevented in the present invention by relieving the bottom of the groove at D adjacent to the gudgeon pin bosses. Tn 'most cases also it is necessary or desirable, as stated, that there should be no slits in the skirt on the sides which contain the gudgeon pin bosses.

Tt will be clear that, as the slrirt is of considerably less diameter than the cylinder bore, and the ring E when in place and compressed is only equal to, or slightly less than, the cylinder bore, the skirt does not require to be compressed or reduced in diameter when the piston is being fitted to the cylinder, only the ring E requiring to be com-. pressed as is usual.

Tn'the construction shown in Figures 6 and 7, where the piston is of extreme shortness as it possesses no actual shirt, the wall is split at B in the same manner as in the construction just described, and there is a re lieved groove D containing the bearing ring Ti], but this groove is located in the horizontal plane containing the gudgeon pin G.

The pin is notched at the ends at G and the;

ring E lies in these notches but it does not bear against the bottom of the notches. The ring in also prevents the gudgeon pin G from working sideways to such an extent as to come into contact with the cylinder wall represented by the broken line Z, and it also'prevents the ring from twisting.

A further feature arising from the provision of a clearance under the bottom of the ring on the faces containing the gudgcon pins, is that'these parts of the piston are free to expand radially slightly without set ting up any binding. As stated, with short pistons it is not possible, or advisable, to split the skirt near the gudgeon pin bosses. Consequently a great deal oi. the, expansion of the metal which takes place at these points must be radially outwards. Til the piston ring beds in the groove the whole way round, this outward expansion causes the ring to be pinched between the piston skirt and the cylinder wall, which clearly causes binding and, in severe cases, actual seizure.

eonor/o An alternative to relieving the bottom of the groove is, of course, to make the ring thinner on those parts which lie on the faces containing the gudgeon pins. Where the ring is pinned to prevent its rotation it would be a simple matter to keep the thin parts of the rings in the required positions. Tt is, however, preferable to increase the depth of the grooves rather than to thin the ring at two points.

llvhat T claim as my invention and desire to secure by Letters Patent of the United States is I l. The combination with an engine piston of a split bearing ring thereon which has a clearance from the piston on the nonpressure faces only of the piston.

2. Tn a piston, the combination of a shirt, longitudinal slits in said skirt, a groove encircling the skirt, and a split bearing ring in said groove and bottoming therein only on the sides forming the pressure faces of the piston, substantially as set forth.

3. Tn a piston, the combination of a skirt, longitudinal slits in said skirt, a groove encircling the skirt, and a split bearing ring located in said groove and bottoming therein except on those sides of the piston which contain the gudgeon pin bosses.

d. Tn a piston, the combination of a skirt, a groove encircling said skirt, a bearing ring located in said groove and bottoming t erein only on the sides forming the pressure faces of the piston, and longitudinal slits in those sides only of the skirt which form the pressure laces, substantially as set forth.

5. Tn a piston, the combination of a shirt, longitudinal slits in said skirt, a groove of varying depth encircling the skirt, and a split bearing ring located in said groove and bottoming therein only on the sides forming the pressure faces of the as set forth.

6. Tn a piston, the combination of a groove extending around it in the plane of the gudgeon pin, a split bearing ring located in said groove bottoming only upon the sides forming the pressure faces of the piston, and

notches formed in the ends of the gudgeon pin which are engaged by said bearing ring. substantially as set forth.

Tn testimony whereof T have signed my F name to this specification in the presence oi" two subscribing witnesses.

AlllfiCblllltALlll) lill'illllll llilllllTGlllPfllEllY .Tlllillll WARE. Witnesses C. T. Krnosrnnn, G. G.

piston, substantially llll 

